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.TH WCSTOD 3C "Apr 21, 2021"
.SH NAME
wcstod, wcstof, wcstold, wstod, watof \- convert wide character string to
floating-point number
.SH SYNOPSIS
.nf
#include <wchar.h>

\fBdouble\fR \fBwcstod\fR(\fBconst wchar_t *restrict\fR \fInptr\fR,
     \fBwchar_t **restrict\fR \fIendptr\fR);
.fi

.LP
.nf
\fBfloat\fR \fBwcstof\fR(\fBconst wchar_t *restrict\fR \fInptr\fR,
     \fBwchar_t **restrict\fR \fIendptr\fR);
.fi

.LP
.nf
\fBlong double\fR \fBwcstold\fR(\fBconst wchar_t *restrict\fR \fInptr\fR,
     \fBwchar_t **restrict\fR \fIendptr\fR);
.fi

.LP
.nf
\fBdouble\fR \fBwstod\fR(\fBconst wchar_t *\fR\fInptr\fR, \fBwchar_t **\fR\fIendptr\fR);
.fi

.LP
.nf
\fBdouble\fR \fBwatof\fR(\fBwchar_t *\fR\fInptr\fR);
.fi

.SH DESCRIPTION
The \fBwcstod()\fR, \fBwcstof()\fR, and \fBwcstold()\fR functions convert the
initial portion of the wide-character string pointed to by \fInptr\fR to
\fBdouble\fR, \fBfloat\fR, and \fBlong double\fR representation, respectively.
They first decompose the input wide-character string into three parts:
.RS +4
.TP
1.
An initial, possibly empty, sequence of white-space wide-character codes (as
specified by \fBiswspace\fR(3C))
.RE
.RS +4
.TP
2.
A subject sequence interpreted as a floating-point constant or representing
infinity or NaN
.RE
.RS +4
.TP
3.
A final wide-character string of one or more unrecognized wide-character
codes, including the terminating null wide-character code of the input
wide-character string.
.RE
.sp
.LP
Then they attempt to convert the subject sequence to a floating-point number,
and return the result.
.sp
.LP
The expected form of the subject sequence is an optional plus or minus sign,
then one of the following:
.RS +4
.TP
.ie t \(bu
.el o
A non-empty sequence of decimal digits optionally containing a radix character,
then an optional exponent part
.RE
.RS +4
.TP
.ie t \(bu
.el o
A 0x or 0X, then a non-empty sequence of hexadecimal digits optionally
containing a radix character, then an optional binary exponent part
.RE
.RS +4
.TP
.ie t \(bu
.el o
One of INF or INFINITY, or any other wide string equivalent except for case
.RE
.RS +4
.TP
.ie t \(bu
.el o
One of NAN or NAN(\fIn-wchar-sequence\fR(\fIopt\fR)), or any other wide string
ignoring case in the NAN part, where:
.sp
.in +2
.nf
n-wchar-sequence:
    digit
    nondigit
    n-wchar-sequence digit
    n-wchar-sequence nondigit
.fi
.in -2

.RE
.sp
.LP
In default mode for \fBwcstod()\fR, only decimal, INF/INFINITY, and
NAN/NAN(\fIn-wchar-sequence\fR) forms are recognized. In C99/SUSv3 mode,
hexadecimal strings are also recognized.
.sp
.LP
In default mode for \fBwcstod()\fR, the \fIn-wchar-sequence\fR in the
NAN(\fIn-wchar-sequence\fR) form can contain any character except ')' (right
parenthesis) or '\e0' (null).  In C99/SUSv3 mode, the \fIn-wchar-sequence\fR can
contain only upper and lower case letters, digits, and '_' (underscore).
.sp
.LP
The \fBwcstof()\fR and \fBwcstold()\fR functions always function in
C99/SUSv3-conformant mode.
.sp
.LP
The subject sequence is defined as the longest initial subsequence of the input
wide string, starting with the first non-white-space wide character, that is of
the expected form. The subject sequence contains no wide characters if the
input wide string is not of the expected form.
.sp
.LP
If the subject sequence has the expected form for a floating-point number, the
sequence of wide characters starting with the first digit or the radix
character (whichever occurs first) is interpreted as a floating constant
according to the rules of the C language, except that the radix character is
used in place of a period, and that if neither an exponent part nor a radix
character appears in a decimal floating-point number, or if a binary exponent
part does not appear in a hexadecimal floating-point number, an exponent part
of the appropriate type with value zero is assumed to follow the last digit in
the string. If the subject sequence begins with a minus sign, the sequence is
interpreted as negated. A wide-character sequence INF or INFINITY is
interpreted as an infinity. A wide-character sequence NAN or
NAN(\fIn-wchar-sequence\fR(\fIopt\fR)) is interpreted as a quiet NaN. A pointer
to the final wide string is stored in the object pointed to by \fIendptr\fR,
provided that \fIendptr\fR is not a null pointer.
.sp
.LP
If the subject sequence has either the decimal or hexadecimal form, the value
resulting from the conversion is rounded correctly according to the prevailing
floating point rounding direction mode. The conversion also raises floating
point inexact, underflow, or overflow exceptions as appropriate.
.sp
.LP
The radix character is defined in the program's locale (category
\fBLC_NUMERIC\fR). In the POSIX locale, or in a locale where the radix
character is not defined, the radix character defaults to a period ('.').
.sp
.LP
If the subject sequence is empty or does not have the expected form, no
conversion is performed; the value of  \fInptr\fR is stored in the object
pointed to by \fIendptr\fR, provided that  \fIendptr\fR is not a null pointer.
.sp
.LP
The \fBwcstod()\fR function does not change the setting of \fBerrno\fR if
successful.
.sp
.LP
The \fBwstod()\fR function is identical to \fBwcstod()\fR.
.sp
.LP
The \fBwatof\fR(\fIstr\fR) function is equivalent to \fBwstod(\fR\fInptr\fR\fB,
(wchar_t **)NULL)\fR.
.SH RETURN VALUES
Upon successful completion, these functions return the converted value. If no
conversion could be performed, \fB0\fR is returned.
.sp
.LP
If the correct value is outside the range of representable values,
\fB\(+-HUGE_VAL\fR, \fB\(+-HUGE_VALF\fR, or \fB\(+-HUGE_VALL\fR is returned
(according to the sign of the value), a floating point overflow exception is
raised, and \fBerrno\fR is set to \fBERANGE\fR. \fBHUGE_VAL\fR,
\fBHUGE_VALF\fR, and \fBHUGE_VALL\fR are described in \fBmath.h\fR(3HEAD).
.sp
.LP
If the correct value would cause an underflow, the correctly rounded result
(which may be normal, subnormal, or zero) is returned, a floating point
underflow exception is raised, and \fBerrno\fR is set to \fBERANGE\fR.
.SH ERRORS
The \fBwcstod()\fR and \fBwstod()\fR functions will fail if:
.sp
.ne 2
.na
\fBERANGE\fR
.ad
.RS 10n
The value to be returned would cause overflow or underflow.
.RE

.sp
.LP
The \fBwcstod()\fR and \fBwcstod()\fR functions may fail if:
.sp
.ne 2
.na
\fBEINVAL\fR
.ad
.RS 10n
No conversion could be performed.
.RE

.SH USAGE
Because 0 is returned on error and is also a valid return on success, an
application wishing to check for error situations should set \fBerrno\fR to 0
call \fBwcstod()\fR, \fBwcstof()\fR, \fBwcstold()\fR, or \fBwstod()\fR, then
check  \fBerrno\fR and if it is non-zero, assume an error has occurred.
.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
l | l
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	T{
\fBwcstod()\fR, \fBwcstof()\fR, and \fBwcstold()\fR are Standard.
T}
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.BR iswspace (3C),
.BR localeconv (3C),
.BR scanf (3C),
.BR setlocale (3C),
.BR wcstol (3C),
.BR math.h (3HEAD),
.BR attributes (7),
.BR standards (7)
